[ubuntu] Ubuntu 14.04 Server MDADM add disk to Raid0 array

Hi I was hoping to get some advice from the experts.

I have a 2 disk mdadm raid0 array. I want to add another disk to it. Many hours of googleing and reading man etc. led me to believe this was a perfectly acceptable thing to do. Seems logical that you might want to extend your array by adding more storage!

I am not worried about the content of the drives as I can recreate this data. It is Raid 0 for performance. It will probably end up with 4 drives as requirement grows.

I issued the following command.
~$ sudo mdadm --grow /dev/md0 --level=0 --raid-devices=3 --add /dev/sdd1
mdadm: level of /dev/md0 changed to raid4
mdadm: added /dev/sdd1
mdadm: Need to backup 3072K of critical section..

It seems to have changed my array to Raid 4 array.

$ cat /proc/mdstat
Personalities : [raid0] [raid6] [raid5] [raid4]
md0 : active raid4 sdd1[3] sdb1[0] sdc1[1]
3907025920 blocks super 1.2 level 4, 512k chunk, algorithm 5 [4/3] [UU__]
[=>...................] reshape = 5.3% (105329668/1953512960) finish=820.2min speed=37552K/sec

Man suggests that this is normal behaviour and it is going to change to Raid 4 add the disk(s) and then change back to Raid 0.

From 2.6.35, the Linux Keel is able to convert a RAID0 in to a RAID4
or RAID5. mdadm uses this functionality and the ability to add devices
to a RAID4 to allow devices to be added to a RAID0. When requested to
do this, mdadm will convert the RAID0 to a RAID4, add the necessary
disks and make the reshape happen, and then convert the RAID4 back to
RAID0.
Can anyone tell me if this is likely to succeed as you can see it is going to take a while to reshape to Raid 4. I presume then the same amount of time to reshape to Raid 0!

Any help appreciated. If @rublylaser is out there I would be interested in your opinion Zak.

I also noticed that the version of mdadm ruing on my 14.04 server is 4 years out of date! and was only installed recently.

Cheers
Spart